Television system



Dec. 6, 1932. A. KAROLUS 1,889,990

TELEVISION SYSTEM Filed Nov. 30, 1928 RECE/ V5? INVENTOR AUGUST KAROLU$ A/aw.

ATT NEY Patented Dec. 6, 1932 PATENT @FFEQE AUGUST KABOLUS, OF LE-IPZIG, GERMANY, ASSIGNOR T RADIO CORPORATION OF AMERICA, A CORPORATION OF DELAWARE I TELEVISION SYSTEM Application filed November 30, 1928, Serial No. 322,756, and in Germany December 31, 1927.

Among the various forms of electric dis charge, cathode rays seem most suitable for receiving work in picture telegraphy because they are readily influenceable by simple electric means. While, on the one hand, their defiectibility by electric or magnetic fields insures the movement of a light spot produced thereby upon a screen for the purpose of picture recomposition without any mechanical- ;Q ly moved means, the intensity control of a pencil or bundle of cathode rays for varying the brightness of the ensuing fluorescent spot by the incoming current or potential variations, on the other hand, is perfectly free from inertia.

For television receiver apparatus, the use of cathode ray tubes, especially in the form of the Braun tube, for example the type disclosed by Nicolson Patent No. 1,47 0,696, has

therefore been often suggested because with one and the same electron ray or pencil, both space control or motion in picture composition as well as brightness control are accomplishable. This would result in a very simple receiver in which the incoming picture could be viewed directly upon the fluorescent screen mounted in the tube, the best and most faithful reproduction of the brightness values of the outgoing picture in this scheme being pro- 39 duced by those light control or valve means which are brought to directly act upon the electron current issuing from the cathode.

The present invention starts from the consideration and an understanding of the fact that those arrangements in which one and the same pencil of cathode rays is to be influenced both for the purpose of picture composition and of brightness control must fail to fulfill the desired end for the following reason:

The means provided to control the light intensity of the fluorescent spot, that is, the strength of the electron current, alterat the same time the velocity of the electrons. However, this fact makes the deviation of the electron ray by the electric or magnetic fields rather uncertain inasmuch as the deflection is a function of the electron speed. The re sult is that the migration or travel of the light spot upon the fluorescent screen fails to be in exact synchronism with the exploration of the pictureat the sending end.

In order to obviate this inconvenience, the cathode ray pencil in the Braun tube according to the present invention, is controlled by crossed fields in well known manner only for the movement or travel of the light spot upon the fluorescent screen, in synchronism and phase with the exploration of the picture at the sending end, while the brightness control is eflected by the aid of another inertialess means having an optical outfit of such a kind that through the same the light spot can be viewed during its motion over the screen of the tube. In this arrangement, as will be noted, only such fractions of the light spot travelling over the screen and being of con stant brightness will reach the eye of the viewer as correspond to the instantaneous values of the incoming values of the incoming current and thus to the brightness values of the respective picture points or elements in the sending picture; in other words, the eye is able to perceive again the incoming picture directly on the screen of the Braun tube. Also in this scheme, the well known Kerr cell, such as is disclosed by my United States patent application, Serial No.l3,338, filed June 2, 1925, based upon electric birefringence or double refraction and being perfectly free from sluggishness will be found most suited for this purpose.

Inasmuch as this arrangement is free from internal control of the intensity of the electron current, the velocity of the electrons will no longer be acted upon since the accelerating potential of the electrons can be kept at a constant value. The movement of the light spot uponthe fluorescence screen which now depends only upon the external control fields will thus be rendered entirelycertain and will be able to-exactly'follow the exploring process at the sending end.

The invention has been illustrated in one of its preferred forms by the accompanying drawing.

Now making reference to the accompanying drawing one embodiment of the invention in which, from the sending side, the image tone frequencies, as well as the two constant 100 serted between the light polarizing prisms 4:

and 5 and through which is directed the eye 6 of the image screen 7 of Braun tube 8. The cathode rays are emitted within the Braun tube from heated electrode 9,'and, for the purpose of keeping the electrons close together, the cathode 9 is surrounded by a static eld 10. The anode member 11 is, provided at its center with an aperture through which the electrons accelerated by the potential ofdirect current source 16 flow in one beam.

. In order to increase the striction of the beam any known means such as filling in of gas of very low. pressure or striction coils as disclosed by N icolson Patent 1,47 0,696, may

be provided. The heated electrode 9 is heated by battery 15 through adjustable resistance 14. 12, 12 and 13, 13 indicate the pairs of deviating plate provided for controlling the motion in space of the cathode rays. These plates 12 and 13 are arranged at right angles to each other. The control frequencies, after being received and suitably amplified, are impressed upon the pairs of plates 12 and 13 through conductors 17 and 18 connecting the receiving apparatus 2 with the cathode. ray position controlling plates 12 and 13.

In this arrangement a dot of light upon screen 7 emits, for, the naked eye, during its motion, a constant brightness, whereas if itis viewed through the Kerr cell 3, the brightness appears to be locally'co'ntrolled in accordance with the corresponding light intensity of the corresponding dot in the picture transmitted, and it is thus seen that the intensity control is provided by an inertialess light value'which is external to, but associated with, the Braun tube which has no light control element.

Having now described my invention, what I claim is: 1 1. A receiving arrangement for television systems including a Braun tube for producing cathode rays, means associated with the said Braun tube for controlling the position of the said generated cathode rays, and an inertialess light valve external to the said Braun tube for regulatingthe observed intensity of the rays produced.

2. In a television receivingsystem, a receiving arrangement, a Braun tub-e, means associated with the said tube for producing cathode rays, means associated with said Braun tube and controlled from said receiv ing the position in space of thesaid cathode receiving device, a'Bra'un tube and means as-' sociated therewith for producing cathode rays, means positioned within said Braun tube and actuated by said signal receiving device for controlling the-'positionof the said cathode rays, means for directing the said position controlled cathode rays externally to said tube, an inertialess lightQvalve through which said externally controlled lightrays" are passed as polarized rays, and means provided by said inertialess light valve and 'controlled in accordance with received signals for doubly refracting said polarized rays and controlling their intensity.

4. In combination, a Braun tube, 9. Kerr cell, and a signal receivlng dev ce, means assoolat-ed wlth said Braun tube for'producing' cathode rays and controlling. the posit-ion'of said rays in accordance with signals received in said receiving device, means for passin said positioned controlled rays throu h sai Kerr cell for observation, and means or controlling the intensity of said rays passing through said Kerr cell in accordance with signals received on'said receiving device.

5. A system for receiving televisionsignals and maintaining synchronism between the point for point intensity of signals and the positioning thereof, which includes meansfor' receiving signals, a Braun tube, and means associated therewith for producing cathode rays and controlling the same within the said tube as to their pos tion 1n 2LCCOICl3.I1C6'W1l3h ived signal pulses, and an inertialess light valve external to said Braun tube for con-' trolling the observed intensity of the position received signals, I whereby the effects. of changes in speed in the electronic stream :of said cathode rays within said tube fllflfiVOlde ed and thesaid rays are controlled in synchronism as to both position andintensity,

6.'An electrooptical image forming ,sys

tem comprising means for'generating a' oath; V

ode beam, means for causing said beam to successively energize the elemental areas of a fluorescent screen, and a light valve under control of incoming image currentjfor viewing said screen. I p

7. The method of producing, at a receiving point, television images of an object at the,

transmitter, which comprises scanning line series of elemental areas of a screen with a stream of material particles at the receiving point in synchronism with the scanning at the transmitter, producing llght of constant so if" controlled cathode rays in accordance with i intensity by the efiect of said particles upon said screen, transmitting light of constant intensity from said screen through a light valve, and controlling said light valve by current received from the transmitter.

8. A television receiving system comprising means for generating an electronic beam, a fluorescent screen on which said beam impinges, means for causing said beam to traverse adjacent line series of elemental areas of said screei meansfor receiving incoming image currents, and light valve receiving light from said screen and being energized by said incoming image currents.

9, The method of viewing uncontrolled in tensity light points on the end wall of a cathode ray tube as controlled intensity light points which comprises developing a cathode ray to produce recurring li ht points on the fluorescent end wall of the tube according to a predetermined pattern of traversal and electrically eclipsing the produced light intermediate the plane of production and the plane of observation to produce effects of light and shadow therein.

10. lhe method of producing television images of an object at a transmitter which comprises electrically scanning recurrent line series of elemental areas of a fluorescent body at the receiving point in synchronism with similar scanning operations at a transmitter, causing light of constant intensity to be emitted from the fluorescent body at each area scanned, transmitting the produced light of constant intensity from the body, and electrically eclipsing in accordance with received image signals the light issuing from the fluorescent body so as to produce image representations.

11. A television receiving system comprising means for causing light to be emitted from the elemental areas of a light field in; the same sequence as the corresponding portions of the field of view at the transmitter are scanned, said light being of the same intensity for each elemental area and radiating with about the same intensity throughout a wide solid angle, a light valve for directly viewing said light field from a point lying within all of said angles and at such a distance from said field that only a small part of the light therefrom enters said valve, and means for controlling said light valve by incoming image currents.

12. A television receiving system comprising a light field in the form of a stationary screen, means for causing light to be emitted from the elemental areas of said screen in the same sequence as the corresponding portions of the field of view at the transmitter are scanned, said light being of the same intensity for each elemental area and radiating with about the same intensity throughout a wide solid angle, a light valve for viewing said screen from a point lying within all of said angles and at such a distance from said screen that only a small part of the emitted light enters said light valve, and means for controlling said light valve by incoming image currents.

18. The method of television which comprises causing light to be emitted from the elemental areas of a light field in the same sequence as the corresponding areas of the field of view at the transmitter are scanned, said light being of the same intensity for each elemental area and radiating with about the same intensity throughout a wide solid angle, viewing said light field from a point lying within all of said angles and at a distance from said light field, and controlling in accordance with the incoming image current and substantially at the observing point the amount of light entering the eye of the observer by means of a light valve, whereby the valve controls only a small fraction of the emitted light.

14. A television receiving system comprising a receiving screen, means for causing the the elemental areas of said screen to emit light in succession of the same intensity, a Kerr cell through which only a small part of the light from each of said elemental areas passes, and means to control said cell in accordance with variations in received image current.

AUGUST KAROLUS. 

